Mixed complex aluminum soap-clay grease composition

ABSTRACT

Grease having previously unachieved outstanding properties of high temperature and mechanical characteristics are prepared by the use of a mixed-base thickener of aluminum complex soap and cation-modified clay.

United States Patent Inventor Arthur T. Polllhuk Media, Pa.

App]. No. 742,155

Filed July 3, i968 Patented Nov. 16, 1971 Assignee Sun Oil Company Philadelphia, Pa.

MIXED COMPLEX ALUMINUM SOAP-CLAY Primary Examiner- Daniel E. Wyman Assistant Examineri. Vaughn Artameys-George L. Church, Donald R. Johnson, Wilmer E.

McCorquodale, Jr. and Kenneth H. Johnson ABSTRACT: Grease having previously unachieved outstanding properties of high temperature and mechanical characteristics are prepared by the use of a mixed-base thickener of aluminum complex soap and cation-modified clay.

MIXED COMPLEX ALUMINUM SOAP-CLAY GREASE COMPOSITION The present invention relates to improved grease compositions. More particularly it relates to grease compositions having exceptional mechanical and thermal properties wherein the improvement arises from a unique mixed-base thickener.

Aluminum complex greases are well known and have been established as greases having generally superior properties. Clay-based greases are also well known. Such clay-based greases have excellent resistance to high temperatures. It is substantially impossible to melt such greases, however, the clay-based greases have not received favorable acceptance. It is the general view of those who use greases such as the automotive industry that clay-based greases cause greater wear than soap-based greases because of the abrasive nature of the clay. Another often-voiced criticism of the clay-based greases is their mechanical breakdown in extended use. This occurs in two principal ways First, by breakdown in the grease structure due to shearing forces and secondly, by the separation of oil from the clay thickener. In the latter case, the grease forms a hard cake with essentially no lubricating properties. Aluminum complex soap greases on the other hand, are not as susceptible to these shortcomings and have been widely accepted. in addition, aluminum complex greases have excellent water resistance whereas clays generally are considered to absorb water. A more complete discussion of the various aspects of clay based grease can be found in Manufacture and Application of Lubricating Greases," Boner, C. 1., Reinhold Publishing Corp., New York City, lst Ed. 1954, Ch. 1?, pgs. 677-755.

in one view, the present invention relates to a complex aluminum soap grease having improved high-temperature and extreme pressure properties as a result of the incorporation therein of a small amount of a clay.

In another view the present invention relates to a novel and unique grease composition comprising mineral lubricating oil thickened to grease consistency with a mixture of complex aluminum soap and a clay.

Briefly stated, the present invention is a mixed-base grease composition comprising a major amount of a mineral lubricating oil thickened to grease consistency with a minor amount of a thickening agent comprising a mixture containing l a complex aluminum soap of an aliphatic carboxylic acid containing l2-25 carbon atoms and an aromatic carboxylic acid containing not more than 10 carbon atoms and (2) a cation-modified clay.

What has been observed in regard to the novel aluminum complex soap-clay greases of the invention is that rather than any of the weakness of either individual grease being magnified, the thickening agents work in close harmony and almost perfect concordance to produce greases of superior character to either individual grease.

The present grease compositions contain a major amount, i.e., over 50 percent of oil and a minor amount, i.e., less than 50 percent of a thickener comprising a mixture of a complex aluminum soap and a cation-modified clay. Herein the percentages and amounts are based on the total weight of oil, complex aluminum soap and cation-modified clay unless specified otherwise. The total amount of thickener employed can vary depending on the intended use to which the grease is to be put, and generally will be in he range of 1-25 wt. per cent. in any event, the amount of thickener used will be suffi cient to thicken the oil to grease consistency.

The amount of cation-modified clay to be used can also be varied depending on he intended use and the desired intensity of a particular set of properties. The improvements noted previously can be obtained by greases wherein the thickener contains from 5 to 95 wt. percent of the cation'modified clay. Preferably, however, the grease will contain to 50 wt. percent and more preferably to 50 wt. percent of the cationmodit'ied clay.

in addition to the thickener mixture, the grease can contain function materials such as antioxidants, EP additives, stabilizers, additives that improve water washoff, such as, atactic polypropylene, ethylene-vinyl acetate copolymer and the like.

The oil component of the compositions is a mineral lubricating oil. The oil can be paraffinic, naphthenic, or aromatic and could have been prepared by conventional petroleum-refining techniques such as, solvent extraction, sulfuric acid treatment, clay treatment, etc. Normally, the oil used will have a viscosity at F. of 505,000 S.U.S. and a VI of 0-130. However, this thickener system will perform equally well in synthetic oil systems, such as, diesters, polyphenyl ethers, silicone oils, and the like.

The complex aluminum soaps useful in preparing greases are described in US. Pat. No. 2,768,138 to Hotten and Echols, issued Oct. 23, 1956. By a complex aluminum soap is meant, an aluminum soap containing O.8l.5, preferably 1.0-].5, hydroxyl anions per aluminum cation and, at least, two dissimilar carboxylic acid anions. Any individual molecule of the complex aluminum soap consists of one trivalent aluminum cation and three monovalent anions. These anions are selected from the group consisting of hydroxyl anions, relatively oil-soluble carboxylic acid anions, and relatively oil-insoluble carboxylic acid anions. A relatively oil-soluble anion (e.g., stearate) is one in which the aluminum disoap of the anion (e.g., aluminum distearate) has a solubility in the oil component of the grease of at least 5 percent at 400 F. Such anions are preferably obtained from aliphatic carboxylic acids containing 12-25 carbon atoms, examples of such acids being stearic acid, palmitic acid, linoleic acid, tall oil acids, and 12- hydroxystearic acid. A relatively oil-insoluble anion (e.g., benzoate) is one in which the aluminum disoap of the anion (e.g., aluminum dibenzoate) has an oil solubility of less than I percent at 400 F. Such anions are preferably obtained from aromatic carboxylic acids containing not more than 10 carbon atoms, examples of such acids being, benzoic acid, toluic acid and ethylbenzoic acid. The preferred complex aluminum soap is aluminum benzoate stearate.

If desired, a mixture of relatively oil-soluble anions and relatively oil-insoluble anions can be used. That is, all the relatively oil-soluble anions do not have to be obtained from the same aliphatic carboxylic acid and all the relatively oil-insoluble anions do not have to be obtained from the same aromatic carboxylic acid.

it is recognized that all the individual soap molecules may not be the same. One soap molecule may contain two hydroxyl anions and one relatively oil-insoluble anion. Another molecular may contain two relatively oil-insoluble anions and one relatively oil-soluble anion. If mixtures of either relatively oilsoluble anions or relatively oil-insoluble anions are used, further variations between individual soap molecules are possible. In the average soap molecule, however, each of the three types of anions will be present. 7,

As is mentioned in the aforesaid Hotten and Echols patent, the ratio of oil-insoluble anions to oil-soluble anions in the complex aluminum soap will usually be in the range of 0.2: l to 5:1, more frequently 0.3:] to 3:], the actual ratio being selected so as to obtain the desired dispersibility of the soap in the oil. As the aromaticity of the base oil increases, the ratio of oil-insoluble anions to oil-soluble anions will generally increase and as the aromaticity decreases this ratio will normally decrease. Preferably the ratio of oil-insoluble anions to oilsoluble anions is in the range of 5:1 to 2:0. 1.

in the compositions of this invention, the aluminum soap can be prepared in the presence of the oil from a substituted cyclic aluminum oxide trimer. The substituted cyclic aluminum oxide trimer has the general formula wherein R is either an alkoxy anion (RO) of an alcohol containing up to 10 carbon atoms or is an acylate anion (RCOO-) of an aliphatic monocarboxylic acid containing 12-22 carbon atoms. These trimers are believed to react with additional carboxylic acids to form the complex aluminum soap.

The substituted cyclic aluminum oxide trimers are described in detail in U.S. Pat. No. 2,979,497 to Rinse, issued Apr. 11, 1961. As described in this patent, an aliphatic monocarboxylic acid, an aluminum alkoxide, and water are admixed and held at a temperature of l76248 F. until formation and liberation of alcohol ceases, after which the temperature is raised to and maintained at about 356 F. until further formation and liberation of alcohol ceases. The product is the substituted cyclic aluminum oxide trimer. The substitutions will be either acylate or alkoxy anions depending upon the mol ratios of the reactants used. For example, if the mol ratio of acid to aluminum alkoxide to water is 1:1:1, the product will be the triacylate cyclic aluminum oxide trimer.

(ac late) l.

I (acylate)-Al ilk-(acylate) If the mol ratio of acid to aluminum alkoxide to water is 2:323, the product will be the diacylate alkoxy cyclic aluminum oxide trimer,

(acylate) (alkoxy) -1il Jil- (acylate) Reaction 1 REACTION 2 i1 0 O CgH1O)Al fil -(6 711135000) 017113500011 3CH COOH l Heat 3Al(CnH;COO) (CuHsCOO) (OH) C H- OH The substitutions on the cyclic aluminum oxide trimers can be a mixture of acylate anions and alkoxy anions, as in the above examples, or can be all acylate anions or all alkoxy anions. Differences in substitutions affect only the amounts of other acids required to complete the reaction. Furthermore, the acylate anions on the trimer do not have to correspond to the particular aliphatic carboxylic acid used. Thus, a trimer containing stearate anions can be reacted with palmitic acid and benzoic acid.

The aliphatic anions of the soap are derived from an aliphatic acid per se or from the trimer or from both. The aromatic anions are derived from an aromatic acid and the aluminum cations of the soap are derived from the trimer. The amount of aliphatic acid and aromatic acid to be reacted with the trimer should be such that the ratio of the aliphatic anions, including those present in the trimer, plus the aromatic anions to aluminum cations is in the range of :1 to 3.0: 1, preferably 1.8:1 to 2.6: 1. Thus, as the number of aliphatic substitutions on the trimer increases, the total amount of carboxylic acid required is reduced. This is apparent also from an examination of reactions 1 and 2 hereinbefore. in reaction I, 5 mols of carboxylic acid are theoretically required to react with i a mol of trimer containing one aliphatic substitution whereas in reaction 2, 4 moles are theoretically required to react with a mol of trimer containing two aliphatic substitutions.

The clay portion of the thickener mixture is a cationmodified clay the preparation of which is shown in U.S. Pat. No. 2,531,427 to Hauser, issued Nov. 28, 1950. The clays which are useful as starting materials are those exhibiting substantial base-exchange properties, and particularly those exhibiting comparatively high base-exchange properties and containing cations capable of more or less easy replacement.

The clays particularly contemplated by the specification and the claims, include the montmorillonites, viz, sodium, potassium, lithium, and other bentonites, viz, Wyoming and/or California bentonite, magnesium bentonite (sometimes called hectorite, Hector, California) and saponite; also nontronite, attapulgite, illite, zeolites, and fullers earth, particularly those of the Georgia-Florida type. These clays, characterized by an unbalanced atomic structure of unbalanced crystal lattice, are believed to have negative charges which are normally neutralized by inorganic cations. As found in nature, therefore, they exist as salts of the weak clay-acid with bases such as the alkalior alkaline-earth metal hydroxides.

The base-exchange capacities of the various clays enumerated run from about 15 to about 100, based upon milliequivalents of exchangeable base per 100 grams of clay. The

montmorillonites have comparatively high base-exchange capacities, viz, -100. Attapulgite and illite have substantial base-exchange capacities, viz, 25-35 and 15-50, respectively. Generally, the clays of higher base-exchange capacities, i.e., of at least 25 are particularly useful where high exchange of an organic base for the cation of the clay is desired.

A clay of the character described and exhibiting substantial base-exchange capacity, is reacted with an organic compound, more particularly one hereinafter generally defined and referred to as an onium compound, by substitution of the clay cation of the organic compound, which cation is of a class hereinafter referred to as an onium" base. An onium compound is defined as a group of organic compounds of the type:

RXl-ly which are isologs of ammonium and contain the element X in its highest positive valency.

The onium base radical exchanged for the inorganic radicals of the clay is hydrophobic as distinguished from hydrophilic, so as to convert the clay from a hydrophilic to an organophilic condition.

A preferred type of onium compound is an organic amine. These compounds may include salts of aliphatic, cyclic, aromatic, and heterocyclic amines, primary, secondary, and tertiary amines and polyamines, also quaternary ammonium compounds. lt has been found that a base with a molecular area of about square angstrom units, for example, a primary amine with a straight aliphatic chain of 10 carbons atoms, e.g., decyl amine, will substantially fulfill the requirements of covering the clay surface. Other types of amines, however, may be used also, e.g., tertiary amines such as, lauryl dimethyl amine. An excess of organic matter as occasioned by use of an amine of area greater than 70 A, as, for example, octadecenylamine, it is not detrimental to the gelling properties of the amine-clay composition. Good results, for instance, have been obtained with primary amines having hydrocarbon chains of 12 or more carbon atoms. The particular type of clay to be used can be varied depending on the intended use. The montmorillonites, bentonite and hectorite are particularly useful, more particularly the bentonites because of their exceptional gellation properties. The novel greases of the present invention can be prepared by preparing a complex aluminum grease and a cation-modified clay grease separately then blending the finished greases in the desired proportions. The greases of the invention can be prepared by blending a complex aluminum grease and a cation-modified clay grease, or the complex aluminum, cation-modified clay grease can be prepared in situ in the same batch of base oil, that is, by forming a mixed base grease directly. The preparation of aluminum complex and modified clay greases generally is well known in the art, for example, the Hotten and Echols patent previously mentioned in regard to complex aluminum greases and U.S. Pat. No. 2,531,440 to Jordan, issued Nov. 28, 1950, in regard to cation-modified clay greases, and needs no discussion here, however, a brief description of the process used for producing the aluminum complex grease from the substituted cyclic aluminum trimer is given.

Conventional equipment can be utilized in the method herein described. Such equipment normally includes a grease kettle equipped with heating facilities and an agitator. Conventional agitators are usually of the paddle type and turn at 15-75 r.p.m. being designed merely to keep the contents of the kettle in motion without creating any areas of very vigorous agitation.

Generally the aliphatic acid is first mixed with a portion of the base lubricating oil and the mixture is heated to a temperature in the range of l80250 F., preferably l90-220 F., at which temperature the trimer is mixed in. The trimer aliphatic acid-base oil mixture is held at this temperature for a period of 5 minutes to 5 hours, preferably 10 minutes to 2 hours. The reaction time should be adjusted to the temperature so that shorter reaction times are employed at higher temperatures.

Alternatively, the aliphatic acid can be mixed with the oil and trimer at a low temperature and the entire mixture then heated up, or the oil can be heated up and both the trimer and acid then mixed in. The order in which the three ingredients are mixed is not critical. The cation-modified clay, can be added at this point, however, it is preferably added just prior to the milling of the grease.

After the trimer and aliphatic acid have reacted, the aromatic acid is mixed in. The aromatic acid should be mixed with the remainder of the base oil and added in liquid phase form and with agitation to the trimer-aliphatic acid phase. Conventional grease kettle agitators, described hereinbefore, will provide sufficient agitation for the proper incorporation of the aromatic acid. The temperature of the mix should be held within the range of l80-250 F while the aromatic acid is being added. Alternatively, the aromatic acid can be added at the same time as the aliphatic acid.

When the incorporation of aromatic acid is complete, the mass should be raised to a temperature in the range of 400-460 F., preferably 410430 F. The time required to reach this temperature is preferably in the range of 1-5 hours, although higher or lower heating periods can also be used. The mass should be maintained at 400-460 F. for a period of 10 minutes to 6 hours, preferably minutes to 2 hours.

After the mass is held at 400-460 F. for the prescribed period, it should be cooled to a temperature in the range of l00-25O F. at which temperature it should be milled. In order to prevent the mass from becoming gelatinous during this cooling step, the cooling should be relatively slow, i.e., it should occur over a period of at least 1 hour. Cooling periods longer than 1 hour can be utilized, but are no t necessary.

Upon cooling to l00-250 F., the mass should be milled. Milling is necessary in order to obtain a grease of uniform composition and which has a smooth and uniform texture.

Conventional milling machines can be used to mill the grease, such as a piston-type mill. Good milling is required for the greases of the present invention thus pressures in the range of 3,0005,000 p.s.i.g. should be used. This is at variance with the aluminum complex greases per se where it is essential that milling pressures not exceed 1,500 p.s.i.g. in order to avoid gelatinous texture in the final product.

if additives such as, oxidation inhibitors, extreme pressure agents, etc. are to be incorporated into the grease, they are preferably added just prior to the milling step, although an antioxidant can be added at the begirining to prevent oxidation of the oil during the heating cycle. The cation-modified clay can also be added at this point. Alternatively, a cationmodified grease is prepared and blended with aluminum complex grease after milling. The following examples are present to illustrate the invention, and at least one of its embodiments.

The oil employed in the examples was a naphthenic oil having the following properties:

Viscosity S.U.S. at F. 500-530 API Gravity at 60 F. i8.$-2l.0

Flash, open cup,

deg. F., 345 Pour point,

deg. F., 5 Conradson carbon 1: 0.07 Neut. Number 0.05 Color ASTM EXAMPLE 1 Preparation Of Aluminum Complex Soap Grease Table II shows the composition of the aluminum complex soap grease employed (grease 1). The grease was prepared by adding to about one-half of the oil the stearic and benzoic acids and the Kolate 65. The mixture was heated to 200-250 F. and stirred at this temperature for about one half hour. The mixture was then heated to about 400 F., while adding the remaining oil. The mixture was then cooled, with stirring to about 150180 F. At this point, the phenyl beta naphthylamine, antioxidant, was added and stirred into the mixture. The mixture was milled at about 1,500 p.s.i.g.

EXAMPLE 2 Preparation Of Bentonite Clay Grease In the preparation of the bentonite clay grease (grease 5 in table 11), about one-third of the oil was mixed with Baragel 24 for about 20-30 minutes. Propylene carbonate was added and mixing continued. The mixture was heated to about 200 F., while adding the remaining oil. The blend was then cooled to F., with stirring and water was added. The antioxidants (PBN) were added and the product milled at 4,000 to 5,000

p.s.i.g.

EXAMPLE 3 Preparation Of Mixed Base Greases The mixed base greases were prepared by blending the greases of examples 1 and 2 in the proportions shown in table 1.

The com po tion of the gaases after blending is shown in table 11.

TABLE [Ir-COMPOSITION OF GREASES k Grease Weight, percent 1 2 3 Stearlc acid 2.6 2. 1 1. 3 Benzolc acid 1. 5 1. 2 0. 8 Kolate 65 6. 2 5. 3. 1 Baragel 24 1. 0 2. 8 Propylene carbonate 0. 1 0. 2 Water Zinc dl-n-butylldlthioearbamate 0.1 0 3 Phenyl beta nephthylamlne (PBN) 0. 0. 4 0. 3 Petroleum oil 89. 2 90. 1 91. 2 91 0 93. 6

Total 100. 0 100.0 100. 0 100.0 100. 0 l5 Trimeric oxy-aluminum dl-alkoxide monoacylcate derived from stearlc acid and aluminum lsopropoxide, trademark of Agrashell, Inc.

2 Reaction product of a sodium montmorillonlte (bentonite clay) and the salt form of a heteroeycllc amine of the structure where R is CHzCHzOH, OH; or CHzCHa and tall 011, trademark of Harold Div., National Lead 00.

3 Used as an anti-oxidant.

iAubtE 4 Testing The prepared greases were subjected to several standard tests for greases. The test and results are shown in table Ill.

TABLE IIL-PHYSICAL PROPERTIES OF MIXED BASE ALUMINUM COMPLEX-BENTONITE CLAY GREASES 1 Based on the wt. of stearlc acid, benzoic acid, and aluminum. 1 ASIM D-l263 is run at only 220 F. whereas the present test was run under more severe temperature conditions.

From the mechanical properties as shown in table Ill it would appear that the bentonite greases are an exception to the previously mentioned weaknesses of clay greases. HOW- ever, these tests are of relatively short duration in comparison to the actual use demanded of grease lubricants. The aluminum complex soap greases do shear to a certain degree initially, reaching a stable point for long-range application whereas the clay based greases including bentonite do not undergo this initial settling in" process, but fail at a point when the equivalent aluminum complex soap grease has a great deal of utility remaining.

it is the principal advantage of the grease compositions of the present invention that clay portion of the thickener contributes its high-temperature properties to the aluminum complex soap grease with no loss in the long-range performance of the aluminum complex soap grease. An added benefit is improvement of the initial properties of the aluminum complex soap grease by the bentonite as can be seen from table ll].

The invention claimed is:

l. A mixed-base grease composition comprising a major amount of a mineral lubricating oil thickened to grease consistency with synergistic proportions of i) an aluminum complex soap of stearic acid and benzoic acid and (2) an onium base cation-modified bentonite clay.

2. A mixed-base grease according to claim 1 where the cation-modified clay is 25 to 50 wt. percent of the thickeners.

3. A mixed-base grease composition according to claim 1 wherein he bentonite clay is modified with the tall oil salt of a heterocyclic amine otthe structure where R is CH CH OH, CH or CHgCHa. 

2. A mixed-base grease according to claim 1 where the cation-modified clay is 25 to 50 wt. percent of the thickeners.
 3. A mixed-base grease composition according to claim 1 wherein the bentonite clay is modified with the tall oil salt of a heterocyclic amine of the structure where R is CH2CH2OH, CH3 or CH2CH3. 